package com.distribute.rpc.registry;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ThreadLocalRandom;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 服务发现
 * @author lxz
 *
 */
public class ServiceDiscovery {
	private static final Logger LOGGER = LoggerFactory.getLogger(ServiceDiscovery.class);
	private CountDownLatch latch = new CountDownLatch(1);
	private volatile List<String> dataList = new ArrayList();
	private String registryAddress;
	
	public ServiceDiscovery(String registryAddress){
		this.registryAddress = registryAddress;
		
		ZooKeeper zk = connectServer();
		if(zk != null){
			watchNode(zk);
		}
	}
	
	public String discover(){
		String data = null;
		int size = dataList.size();
		if(size > 0){
			if(size == 1){
				data = dataList.get(0);
				LOGGER.debug("using only data: {}", data);
			}else{
				data = dataList.get(ThreadLocalRandom.current().nextInt(size));
				LOGGER.debug("using random data: {}", data);
			}
		}
		return data;
	}
	
	private ZooKeeper connectServer(){
		ZooKeeper zk = null;
		try{
			zk = new ZooKeeper(registryAddress, Constant.ZK_SESSION_TIMEOUT, new Watcher(){
				public void process(WatchedEvent event) {
					if(event.getState() == Event.KeeperState.SyncConnected){
						latch.countDown();
					}
				}
			});
			latch.await();
		} catch(IOException e){
			LOGGER.error("", e);
		} catch(InterruptedException e){
			LOGGER.error("", e);
		}
		return zk;
	}
	
	private void watchNode(final ZooKeeper zk){
		try{
			List<String> nodeList = zk.getChildren(Constant.ZK_REGISTRY_PATH, new Watcher(){
				public void process(WatchedEvent event) {
					if(event.getType() == Event.EventType.NodeChildrenChanged){
						watchNode(zk);
					}
				}
			});
			List<String> dataList = new ArrayList();
			for(String node : nodeList){
				byte[] bytes = zk.getData(Constant.ZK_REGISTRY_PATH + "/" + node, false, null);
				dataList.add(new String(bytes));
			}
			LOGGER.debug("node data:{}", dataList);
			this.dataList = dataList;
		} catch(KeeperException e){
			LOGGER.error("", e);
		} catch(InterruptedException e){
			LOGGER.error("", e);
		}
	}
}
